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Solution properties of synthetic polypeptides. XVI. Hydrogen bonding in helix–coil transitions of poly(β‐benzyl L ‐aspartate)
Author(s) -
Norisuye Takashi,
Misumi Kozo,
Teramoto Akio,
Fujita Hiroshi
Publication year - 1973
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1973.360120708
Subject(s) - chemistry , hydrogen bond , intramolecular force , intermolecular force , enthalpy , dichloroacetic acid , solvent , molecule , crystallography , mole , helix (gastropod) , stereochemistry , thermodynamics , organic chemistry , ecology , physics , biology , snail
Helix–coil transition of polypeptides in solution involves two elementary processes: unfolding of an α‐helical polypeptide chain and interaction of the unfolded chain with solvent molecules which are capable of forming hydrogen bonds. Optical rotation data for poly(β‐benzyl L ‐aspartate) in mixtures of dichloroacetic acid and carbon tetrachloride are analyzed according to the procedure developed by Sayama et al., who explicitly took these processes into theoretical account; and the enthalpy changes, Δ H 0 = −650 ± 200 cal/mole and Δ H a = −5.2 ± 1.6 kcal/mole. The latter value is favorably compared with heats of association (per hydrogen bond) of various amides and lactams in CCl 4 . There is excellent agreement with −5.15 kcal/mole for δ‐valerolactam in CCl 4 . In analogy with amides in non‐polar solvents, the difference between Δ H 0 and Δ H a may be attributed to the fact that the former is associated with intramolecular hydrogen bonding, whereas the latter is associated with intermolecular hydrogen bonding.